(1) Field of the Invention
The present invention is directed to a slotted antenna having enhanced broadband characteristics.
(2) Description of the Prior Art
Slotted cylinder antennas are popular antennas for use in line of sight communications systems, especially where the carrier frequency exceeds 300 MHz. FIG. 1 provides a diagram of a prior art slotted cylinder antenna 10. Antenna 10 includes a metallic cylinder 12 having slot 14 cut into the wall of the cylinder 12. Cylinder 12 can be any thickness as long as skin effects are avoided. Slot 14 is parallel to an axis 16 of cylinder 12. In the antenna shown, slot 14 extends the entire length of the cylinder 12. The interior of the cylinder or cavity is typically filled with air but another dielectric material can be used. FIG. 1 shows an end-fed version of this antenna, but this antenna can also be center-fed. In the end-fed version, a transmission line 18 is provided through the cylinder 12 and connected across the slot 14 near one end of the slot 14. Transmission line 18 can be either a balanced line, such as a twisted pair, or an unbalanced line, such as a length of coaxial line (shown). In either case, the feeding transmission line 18 must have two conductors in order to connect across slot 14. The optimal frequency of this antenna is given by the length of the slot. The size of the cavity and the slot width govern bandwidth.